There is no hard limit on maximum interactions per week/month. Contact them whenever you need help and you'll get a reply.
While we don't limit interactions on an application-base, there is of course a natural limit of how often you can and should talk to your mentor. They are busy people and can't check in on you a dozen times per day.
Act naturally - mentors are also humans with their own set of responsibilities and not a search engine. Mutual respect is very important.